This invention relates to apparatus for producing microform records of alpha-numeric, pictorial or digitally coded information.
Microfilm records of documents have, heretofore, been commercially produced by exposing conventional silver halide film, requiring processing with liquid chemicals, with greatly reduced images of the documents involved. Because the processing of the film requires skilled personnel who can handle the processing chemicals and equipment involved, microfilm processing equipment has not been a standard piece of office equipment, like the Xerox-type document copying machines found in most offices today.
Relatively recently, there has been developed films which are imaged solely by application of heat and/or light, making feasible the design of useful microfilm recording equipment operable to make microfilm records directly from hard copy by unskilled office personnel. Such dry process microfilm recording equipment is disclosed in U.S. Pat. No. 3,966,317, granted June 29, 1976. However, there has been a substantial need to produce alpha-numeric and pictorial microfilm records directly from electrical signals generated by a typewriter keyboard or outputed from computers or the like. While it has been proposed to make microfilm records of alpha-numeric or pictorial data directly from electrical signals generated by computers, such equipment has required the use of laser beam film scanning equipment, which is very expensive and wasteful of energy. For example, the cost of such equipment heretofore quoted has been well in excess of $100,000 per machine. Also, OSHA regulations prevent their use in most offices.
In co-pending application Ser. No. 724,084, filed Sept. 16, 1976, a data storage and retrieval system is disclosed which produces directly from a typewriter keyboard or computer output micro-sized, alpha-numeric or pictorial producing, dot image patterns on a dry process dispersion type film, like that disclosed in U.S. Pat. No. 3,966,317. The data storage and retrieval system disclosed in this application utilizes a recording head including micro-sized current-carrying points for Joule heating micro-sized points on such a film which produces similarly sized dot images from the heat applied thereto. The recording heads disclosed in this application, which were developed by me, have unbelievably small, current-carrying, heat-producing points each having dimensions preferably no greater than about 12 micron and, less desirably, no greater than about 20 micron, to produce similarly sized dot images on the recording film. Adjacent portions of these heat-producing points of the recording heads are preferably spaced apart a distance much less than the size thereof so that adjacent dot images can appear almost merged into a continuous image without the need of current pulse profiles causing substantial spreading of the heat and consequent greater cooling times.
The current-carrying, heat-producing points on the recording head are preferably aligned in a single row, and selected ones of these current-carrying points are fed with bursts of short pulses of current as the recording head scans the film, to form the desired pattern of dot images in the film, duplicating the data represented by the current pulses fed to the current-carrying points of the recording heads. The recording heads disclosed in this application, which have current-carrying points formed by fine threads of heating wire material like chromel or nichrome or threads of deposited resistance material, are mounted on a support structure which rapidly causes the threads of heating wire material to scan the film area set aside for a page of data to be recorded thereon at a given moment. While the recording heads disclosed in the drawings of this application have less than 10 such aligned current-carrying points, by providing a recording head with a vertical row of current-carrying heat-producing points thereon equal to the number of dot images-receiving spaces in the entire vertical extent of this area, a full page of data can be recorded in only a single sweep of the area by the recording head involved. During each sweep of the recording head across this area of the film, the various current-carrying heat-producing points of the recording head will be fed with large numbers of current pulses. The permissible scanning speed of such a recording head depends to a great extent on the time it takes each current-carrying, heat-producing point thereof to cool sufficiently following the termination of a current pulse therein that the temperature of the point involved will not create another image on the film until the next current pulse is fed thereto.
Prior to the invention disclosed in application Ser. No. 724,084 it was not thought feasible to produce micro-sized dot images on heat responsive films by Joule heating the same from current-carrying wires or threads of deposited resistance material.
An object of the present invention is to provide a heat-producing recording head capable of producing clearly defined, extremely closely spaced micro-sized, projectible dot images on a heat-responsive film, so that microfilm records can be produced thereby, and the information so recorded can be projected onto a screen by conventional microfilm reading equipment in a manner where the information can be easily read.
Another object of the invention is to provide a recording head having micro-sized, current-carrying, heat-producing points thereon capable of producing micro-sized dot images on a heat-responsive film, and wherein the recording head is constructed to minimize the cooling time of the current-carrying heat-producing points thereof, upon termination of a current pulse fed thereto.
A further object of the invention is to provide apparatus for forming dot images on heat-imageable film with a recording head which makes sliding engagement with the surface of the film in the process of sweeping the same, and wherein any serious scratching of the film is avoided.
A still further object of the invention is to provide a recording head as described, and which is so constructed that it can be manufactured at a reasonable cost. A related object of the invention is to provide a recording head as described which has a relatively long life expectancy.